[Radiotherapy of mobile tumors]

In this article we detail some questions related to managing the treatment of mobile tumors, that is, those tumors that shift with respiratory movements, integrating movement into the plan of treatment. This fact complicates the administration of high doses of radiotherapy since, in such cases, the radiation margin must be wider than that required by the tumor itself, representing a greater risk to surrounding healthy tissue. However, the new technologies offer an alternative in these cases, such as tracking and respiratory gating in radiotherapy (RT), that is, the synchronization of treatment with respiratory movement. In gating we capture the tumor and other organs at risk at a specific moment in the breathing cycle, while in tracking we trace the tumor and the organs at risk throughout the breathing cycle. It is therefore essential to obtain good images and to correlate them with each phase of the breathing cycle. The tumors with which these strategies have been most employed are those of the lung, breast and lymphomas, and less frequently with some abdominal tumors such as pancreas, liver and prostate.